restructure: move bin/ and tests/ to src/

Also add symlinks from the old `bin/` and `tests/` locations to avoid
breaking scripts and other tools.

Motivations:

  * Scripts and tests no longer have to do dubious things like:

        require('ep_etherpad-lite/node_modules/foo')

    to access packages installed as dependencies in
    `src/package.json`.

  * Plugins can access the backend test helper library in a non-hacky
    way:

        require('ep_etherpad-lite/tests/backend/common')

  * We can delete the top-level `package.json` without breaking our
    ability to lint the files in `bin/` and `tests/`.

    Deleting the top-level `package.json` has downsides: It will cause
    `npm` to print warnings whenever plugins are installed, npm will
    no longer be able to enforce a plugin's peer dependency on
    ep_etherpad-lite, and npm will keep deleting the
    `node_modules/ep_etherpad-lite` symlink that points to `../src`.

    But there are significant upsides to deleting the top-level
    `package.json`: It will drastically speed up plugin installation
    because `npm` doesn't have to recursively walk the dependencies in
    `src/package.json`. Also, deleting the top-level `package.json`
    avoids npm's horrible dependency hoisting behavior (where it moves
    stuff from `src/node_modules/` to the top-level `node_modules/`
    directory). Dependency hoisting causes numerous mysterious
    problems such as silent failures in `npm outdated` and `npm
    update`. Dependency hoisting also breaks plugins that do:

        require('ep_etherpad-lite/node_modules/foo')

src/tests/frontend/specs/pad_modal.js

@@ -0,0 +1,131 @@
+'use strict';
+
+describe('Pad modal', function () {
+  context('when modal is a "force reconnect" message', function () {
+    const MODAL_SELECTOR = '#connectivity';
+
+    beforeEach(function (done) {
+      helper.newPad(() => {
+        // force a "slowcommit" error
+        helper.padChrome$.window.pad.handleChannelStateChange('DISCONNECTED', 'slowcommit');
+
+        // wait for modal to be displayed
+        const $modal = helper.padChrome$(MODAL_SELECTOR);
+        helper.waitFor(() => $modal.hasClass('popup-show'), 50000).done(done);
+      });
+
+      this.timeout(60000);
+    });
+
+    it('disables editor', function (done) {
+      expect(isEditorDisabled()).to.be(true);
+
+      done();
+    });
+
+    context('and user clicks on editor', function () {
+      beforeEach(function () {
+        clickOnPadInner();
+      });
+
+      it('does not close the modal', function (done) {
+        const $modal = helper.padChrome$(MODAL_SELECTOR);
+        const modalIsVisible = $modal.hasClass('popup-show');
+
+        expect(modalIsVisible).to.be(true);
+
+        done();
+      });
+    });
+
+    context('and user clicks on pad outer', function () {
+      beforeEach(function () {
+        clickOnPadOuter();
+      });
+
+      it('does not close the modal', function (done) {
+        const $modal = helper.padChrome$(MODAL_SELECTOR);
+        const modalIsVisible = $modal.hasClass('popup-show');
+
+        expect(modalIsVisible).to.be(true);
+
+        done();
+      });
+    });
+  });
+
+  // we use "settings" here, but other modals have the same behaviour
+  context('when modal is not an error message', function () {
+    const MODAL_SELECTOR = '#settings';
+
+    beforeEach(function (done) {
+      helper.newPad(() => {
+        openSettingsAndWaitForModalToBeVisible(done);
+      });
+
+      this.timeout(60000);
+    });
+    // This test breaks safari testing
+    /*
+    it('does not disable editor', function(done) {
+      expect(isEditorDisabled()).to.be(false);
+      done();
+    });
+*/
+    context('and user clicks on editor', function () {
+      beforeEach(function () {
+        clickOnPadInner();
+      });
+
+      it('closes the modal', function (done) {
+        expect(isModalOpened(MODAL_SELECTOR)).to.be(false);
+        done();
+      });
+    });
+
+    context('and user clicks on pad outer', function () {
+      beforeEach(function () {
+        clickOnPadOuter();
+      });
+
+      it('closes the modal', function (done) {
+        expect(isModalOpened(MODAL_SELECTOR)).to.be(false);
+        done();
+      });
+    });
+  });
+
+  const clickOnPadInner = () => {
+    const $editor = helper.padInner$('#innerdocbody');
+    $editor.click();
+  };
+
+  const clickOnPadOuter = () => {
+    const $lineNumbersColumn = helper.padOuter$('#sidedivinner');
+    $lineNumbersColumn.click();
+  };
+
+  const openSettingsAndWaitForModalToBeVisible = (done) => {
+    helper.padChrome$('.buttonicon-settings').click();
+
+    // wait for modal to be displayed
+    const modalSelector = '#settings';
+    helper.waitFor(() => isModalOpened(modalSelector), 10000).done(done);
+  };
+
+  const isEditorDisabled = () => {
+    const editorDocument = helper.padOuter$("iframe[name='ace_inner']").get(0).contentDocument;
+    const editorBody = editorDocument.getElementById('innerdocbody');
+
+    const editorIsDisabled = editorBody.contentEditable === 'false' || // IE/Safari
+                        editorDocument.designMode === 'off'; // other browsers
+
+    return editorIsDisabled;
+  };
+
+  const isModalOpened = (modalSelector) => {
+    const $modal = helper.padChrome$(modalSelector);
+
+    return $modal.hasClass('popup-show');
+  };
+});